外生菌根真菌对杉木的接种效应

对商南县2年生杉木苗木进行乳牛肝菌(Suillus bovines)、褐环乳牛肝菌(Suillus luteus)和褐黄牛肝菌(Boletus luridus)3种外生菌根真菌的接种试验.结果显示,外生菌根真菌对杉木苗木成活率、苗高和地径生长均有明显的促进作用,能明显提高苗木的菌根化水平,增加苗木体内叶绿素含量,促进其游离脯氨酸含量的累积,降低丙二醛含量.对不同坡向杉木苗木各项生长指标的分析显示,在杉木人工造林中,阳坡的综合效应明显优于阴坡.乳牛肝菌和褐黄牛肝菌可作为一种生物肥料,在杉木人工造林中应用.     

辽东栎幼苗的外生菌根合成

 在温室花盆中播种辽东栎（Quercus liaotungensis）种子获得辽东栎幼苗,并对幼苗接种外生菌根真菌进行菌根合成试验。所用的外生菌根真菌有：铆钉菇（Gomphidius viscidus）、臭红菇（Russula foetens）、厚环乳牛肝菌（Suillus grevillei）、褐环乳牛肝菌（S. luteus）、彩色豆马勃（Pisolithus tinctorius）、美味牛肝菌（Boletus edulis）、赭丝膜菌（Cortinarius russus）、土生空团菌（Cenococ     

铝对外生菌根真菌营养元素吸收和酶活性的影响

以褐环乳牛肝菌Suillus luteus (Sl)、乳牛肝菌Suillus bovines (Sb)、琥珀乳牛肝菌Suillus placidus (Sp)为供试菌株,采用液体培养法,分析不同浓度Al³⁺ (0、0.2、0.4、0.8、1.2和1.6 mmol·L^–1)处理对3种外生菌根真菌生物量、pH、养分吸收、抗氧化酶活性、MDA含量的影响,探讨外生菌根真菌耐铝机制。结果表明,铝处理显著增加3种菌株生物量、P含量和Al含量,降低培养液中pH。当Al³⁺浓度为0.8 mmol·L^–1时,菌株生物量增幅最大,各浓度Al³⁺处理的3种菌株Al含量为Sp＞Sb＞Sl;K含量随Al³⁺浓度增加呈先上升后下降的趋势,低浓度Al³⁺(≤0.4 mmol·L^–1)显著促进Sl菌株中N元素的积累,0.4 mmol·L^–1 Al³⁺处理菌株N含量较无铝处理增加42.65%。铝处理还显著降低菌株POD和SOD活性,增加菌株MDA含量。菌株生物量与菌丝N、P、K含量呈极显著正相关(P＜0.01),其中与P含量相关性最高(r=0.635)。综上,环境中Al³⁺浓度是影响外生菌根真菌吸收铝的关键因素,在一定Al³⁺浓度下,外生菌根真菌通过增加对营养元素N、P、K的吸收,提高菌丝酶活性,降低MDA含量以缓解铝毒害,增强其在铝胁迫下的生存能力。该研究为筛选抗(耐)铝性强的优良菌株提供理论依据。     

四种外生菌根真菌对油松幼苗的抗猝倒病和促生作用

为了筛选拮抗油松猝倒病菌及对油松苗木具有促生作用的外生菌根（ectomycorrhizal,ECM）真菌,通过对盆栽油松幼苗进行人工接种,测定了ECM真菌对油松根的侵染率、对猝倒病的防治效果以及对油松株高和地径的影响。结果表明,供试ECM真菌中,绒粘盖牛肝菌Suillus tomentosus、灰环粘盖牛肝菌Suillus laricinus、灰鹅膏菌Amaniata vaginata和血红铆钉菇Gomphidius viscidus可在盆栽条件下与油松合成菌根。灰鹅膏菌对油松猝倒病防治效果最好,为43%     

印度块菌(Tuber indicum)菌根促生细菌的研究

【目的】筛选对印度块菌菌根量和菌根苗长势有促进作用的菌根促生细菌(Mycorrhization helper bacteria,MHB)。【方法】选择华山松为宿主植物,自块菌菌根根际土壤中分离得到的11种细菌为供试菌株,将印度块菌菌剂与不同浓度的细菌混合于特定基质中后接种于华山松上,并通过对印度块菌与华山松形成的菌根数、华山松的株高和地径三方面的统计与分析,确认MHB。【结果】Pseudomonas sp. JCM 5481 (P143)、Streptomyces sp. EN31 (S191)、Variovorax paradoxus (V633)在浓度为2.4×109 CFU/mL时对印度块菌菌根数、株高和地径均有极显著促进作用(P<0.01);Pseudomonas chlororaphis (P11)、Pseudomonas corrugate (P127)在浓度为0.8×109 CFU/mL时对印度块菌菌根数、株高和地径均有显著促进作用(P<0.05)。4种假单胞菌浓度梯度的设置显示了不同菌株适宜的浓度不同。【结论】实验获得5种MHB,并表明细菌浓度是获得MHB的一个重要影响因素。     

6种外生菌根真菌对西南桦幼苗的接种效应

【背景】西南桦是兼具内生、外生菌根的典型菌根营养型树种,菌根化育苗是其壮苗培育的有效措施。【目的】揭示外生菌根真菌对西南桦无性系幼苗生长和养分含量的影响,为其菌根化育苗筛选优良外生菌根真菌提供科学依据。【方法】以BY1、FB4、FB4+和A5等4个西南桦优良无性系为研究对象,选用土生空团菌(Cenococcumgeophilum)、松乳菇(Lactariusdeliciosus)、黄硬皮马勃(Scleroderma flavidum)、多根硬皮马勃(S. polyrhizum)、褐环乳牛肝菌(Suillus luteus)和红绒盖牛肝菌(Xerocomuschrysenteron)6个外生菌根真菌进行盆栽接种试验,分析接种处理间及无性系间苗高、地径、生物量以及养分含量差异。【结果】6个菌种均能与西南桦无性系幼苗形成外生菌根共生体,接种多根硬皮马勃与黄硬皮马勃显著促进了幼苗生长和养分吸收(P0.05),说明其与幼苗的亲和力明显优于其它菌种。尽管菌根侵染率在4个无性系之间无显著差异(P≥0.05),但各菌种对FB4、BY1幼苗生长的促进作用显著强于其它2个无性系。【结论】多根硬皮马勃和黄硬皮马勃可作为西南桦菌根化育苗的优选菌种。     

美味牛肝菌菌塘中菌根促生菌的筛选与鉴定

为了获得黑松Pinus thunbergii-美味牛肝菌Boletus edulis（Be）菌塘中的菌根促生菌（mycorrhiza helper bacteria,MHB）,为美味牛肝菌的人工培育提供理论基础,通过比较野生牛肝菌菌塘细菌胞外代谢产物对菌丝生长的促进作用以及细菌+Be真菌双接处理黑松幼苗对其苗高、地径、茎根比、干重、根侵染率的影响,筛选出菌根促生菌。结果表明,菌株B2和K2代谢产物可以显著促进Be菌丝生长,盆栽实验结果表明双接种Be+B2、Be+K2的黑松苗,苗高分别增长了17.71%和16.82%,地径增长了41.65%和35.63%,干重提高了44.71%和48.78%,根侵染率提高了23.20%和21.50%,茎根比下降了46.41%和35.40%。可见菌株B2和K2是黑松-美味牛肝菌的菌根促生菌。通过细菌的形态、生化特性、16S rDNA序列测定,菌株B2和K2均鉴定为蜡样芽孢杆菌Bacillus cereus。蜡样芽孢杆菌有望进一步开发为美味牛肝菌的菌塘生物肥料。     

盐胁迫下外生菌根真菌与根际有益细菌互作对杨树光合特性的影响

以美洲黑杨幼苗为对象,利用盆栽试验,在100 mmol/L NaCl胁迫条件下研究单接种和双接种外生菌根真菌红绒盖牛肝菌(Xerocamus chrysenteron,简称Xc)、溶磷细菌恶臭假单胞菌(Pseudomonas putida,简称JW-SX1)和菌根辅助细菌蜡状芽孢杆菌(Bacillus cereus,简称HB59)对杨树幼苗的气体交换参数、叶绿素荧光和光响应曲线参数的影响。结果表明:盐胁迫下,接种Xc、JW-SX1及HB59的杨树幼苗净光合速率(Pn)、气孔导度(Gs)、蒸腾速率(Tr)显著增强,且均显著高于对照,而单接JW-SX1和双接Xc+JW-SX1处理的胞间CO2浓度(Ci)低于对照,但与对照相比差异不显著;各接种处理显著增强了杨树的最大光化学效率(Fv/Fm),但处理之间差异不显著性;不同接种处理杨树的实际光化学效率(ΦPSⅡ)与对照(CK)差异不明显,其中接种HB59和Xc+JW-SX1处理分别高于对照14.36%和19.33%;同时接种处理还明显提高了宿主的最大光合速率(Pmax)、光饱和点(LSP)、表观有效利用效率(YAQ),降低了光补偿点(LCP)和暗呼吸速率(RD),且双接种菌根真菌Xc和JW-SX1处理效果更为明显。研究发现,外生菌根真菌、溶磷细菌和菌根辅助细菌可通过改善叶片叶绿素荧光和光合参数、光响应参数来减轻盐胁迫对宿主造成的伤害,从而提高杨树的耐盐性能力。     

青蒿素对外生菌根真菌化感效应

青蒿素是治疗疟疾的首选药物,主要从黄花蒿(Artemisia annua L.)中提取,然而黄花蒿在生长过程中会向周围环境分泌青蒿素。为正确评估青蒿素对森林生态系统中的重要成分""外生菌根真菌的影响,试验以重庆地区有代表性的两株外生菌根真菌——褐环乳牛肝菌(Suillus luteus)Sl 8和松乳菇(Lactarius delicious)Ld 3为材料,研究了青蒿素对菌丝生长,H+和有机酸分泌,以及养分吸收的影响。结果表明,在液体培养基中加入青蒿素,外生菌根真菌的生长受到明显抑制,菌丝生物量降幅高达26.89%(Ld 3)和89.13%(Sl 8);Ld 3分泌H+和草酸的能力增强,而Sl 8分泌量下降。随着青蒿素浓度的增加,菌丝的N、P、K含量及吸收量显著减少。当培养基中青蒿素达到80 mg/L时,Ld 3的N、P、K吸收量比不加青蒿素的处理分别降低了50.55%、46.30%和42.28%;Sl 8几乎丧失对N、P、K的吸收能力。说明青蒿素不同程度地抑制了外生菌根真菌的生长和养分吸收,但对H+和草酸的分泌作用因菌株不同而异。     

氢氧化细菌SDW-16的分离鉴定及促生特性

利用气体循环培养体系从沙打旺根际土壤分离得到1株氢氧化细菌SDW-16(GenBank登录号:KF835389),16S rDNA序列分析和生理生化特征鉴定其为荧光假单胞菌(Pseudomonas fluorescens)。菌株对植物促生机制的初步研究表明菌株SDW-16除具有铁载体分泌能力外,还具有产IAA和ACC脱氨酶活性,其中产IAA量为(21.62±0.30)μg/mL,ACC脱氨酶活力高达(8 372.17±805.43) nmol/(mg·h)。菌株SDW-16具有多项促生能力且均高于其他菌株,说明菌株SDW-16有较高的促生特性,同时也初步证明了氢氧化细菌的促生机制。     

Ectomycorrhizal symbiosis affects functional diversity of rhizosphere fluorescent pseudomonads

Here we characterized the effect of the ectomycorrhizal symbiosis on the genotypic and functional diversity of soil Pseudomonas fluorescens populations and analysed its possible consequences in terms of plant nutrition, development and health. Sixty strains of P. fluorescens were isolated from the bulk soil of a forest nursery, the ectomycorrhizosphere and the ectomycorrhizas of the Douglas fir (Pseudostuga menziesii) seedlings-Laccaria bicolor S238N. They were characterized in vitro with the following criteria: ARDRA, phosphate solubilization, siderophore, HCN and AIA production, genes of N2-fixation and antibiotic synthesis, in vitro confrontation with a range of phytopathogenic and ectomycorrhizal fungi, effect on the Douglas fir-L. bicolor symbiosis. For most of these criteria, we demonstrated that the ectomycorrhizosphere significantly structures the P. fluorescens populations and selects strains potentially beneficial to the symbiosis and to the plant. This prompts us to propose the ectomycorrhizal symbiosis as a true microbial complex where multitrophic interactions take place. Moreover it underlines the fact that this symbiosis has an indirect positive effect on plant growth, via its selective pressure on bacterial communities, in addition to its known direct positive effect.     

New alkane-responsive expression vectors for Escherichia coli and pseudomonas

We have developed Escherichia coli and Pseudomonas expression vectors based on the alkane-responsive Pseudomonas putida (oleovorans) GPo1 promoter PalkB. The expression vectors were tested in several E. coli strains, P. putida GPo12 and P. fluorescens KOB2Delta1 with catechol-2,3-dioxygenase (XylE). Induction factors ranged between 100 and 2700 for pKKPalk in E. coli and pCom8 in Pseudomonas strains, but were clearly lower for pCom8, pCom9, and pCom10 in E. coli. XylE expression levels of more than 10% of total cell protein were obtained for E. coli as well as for Pseudomonas strains.     

Comparative study of 7 fluorescent pseudomonad clinical isolates

There is some debate about the potential survival of Pseudomonas fluorescens at temperatures above 37 degrees C and its consequences for infectious potential, owing to the heterogeneity of clinical strains. Seven clinical strains growing at 37 degrees C or more were submitted for polyphasic identification; 2 were identified as Pseudomonas mosselii and 4 were precisely characterized as P. fluorescens bv. I or II. The binding indexes on glial cells of the strains identified as P. fluorescens bv. I and P. mosselii were compared with that of a reference psychrotrophic strain, P. fluorescens MF37 (bv. V). Clinical P. fluorescens had a similar adherence potential range than strain MF37. Conversely, the binding indexes for P. mosselii strains were 3 times greater than that for strain MF37. These data, and those obtained by comparing the cytotoxic activities of P. fluorescens clinical strains, suggest the existence of different virulence mechanisms, leading either to a low infectious form or to a microorganism with cytotoxic activity in the same range as that of P. mosselii or even Pseudomonas aeruginosa.     

Lysine decarboxylase in Pseudomonas aeruginosa]

The research of lysine, ornithine and arginine decarboxylases has been made for 50 strains of fluorescent Pseudomonas (P. aeruginosa, P. fluorescens, P. putida). By thin layer chromatography, all the strains of Pseudomonas aeruginosa and the fifth of the strains of P. putida had lysine decarboxylase activity at alcaline pH (optimal pH 8) ; Pseudomonas fluorescens did not produce this decarboxylase. Arginine and ornithine decarboxylase are absent for all the strains of fluorescent Pseudomonas.     

Effect of preservation conditions on the diagnostic traits of Pseudomonas aeruginosa, P. fluorescens and P. putida

After 20 years storage under the lyophylized condition 6 strains of Pseudomonas aeruginosa, P. fluorescens and P. putida retained all characters investigated. After storage under sterile vaseline oil for 10 years strains P. aeruginosa and P. putida lost one character, strains P. fluorescens lost 10-13 characters.     

Flagellin gene sequence variation in the genus Pseudomonas

Flagellin gene (fliC) sequences from 18 strains of Pseudomonas sensu stricto representing 8 different species, and 9 representative fliC sequences from other members of the gamma sub-division of proteobacteria, were compared. Analysis was performed on N-terminal, C-terminal and whole fliC sequences. The fliC analyses confirmed the inferred relationship between P. mendocina, P. oleovorans and P. aeruginosa based on 16S rRNA sequence comparisons. In addition, the analyses indicated that P. putida PRS2000 was closely related to P. fluorescens SBW25 and P. fluorescens NCIMB 9046T, but suggested that P. putida PaW8 and P. putida PRS2000 were more closely related to other Pseudomonas spp. than they were to each other. There were a number of inconsistencies in inferred evolutionary relationships between strains, depending on the analysis performed. In particular, whole flagellin gene comparisons often differed from those obtained using N- and C-terminal sequences. However, there were also inconsistencies between the terminal region analyses, suggesting that phylogenetic relationships inferred on the basis of fliC sequence should be treated with caution. Although the central domain of fliC is highly variable between Pseudomonas strains, there was evidence of sequence similarities between the central domains of different Pseudomonas fliC sequences. This indicates the possibility of recombination in the central domain of fliC genes within Pseudomonas species, and between these genes and those from other bacteria.     

Diversity of genetic systems responsible for biodegradation of naphthalene in Pseudomonas fluorescens strains

The genetic systems that are responsible for naphthalene catabolism were analyzed in 18 naphthalene-degrading Pseudomonas fluorescens strains isolated from oil-contaminated soils in different regions of Russia. It was found that thirteen strains contain plasmids, from 20 to 120 kb in size, at least five of which are conjugative and bear the catabolic genes responsible for the complete utilization of naphthalene and salicylate. Five plasmids belong to the P-7 incompatibility group, and two plasmids belong to the P-9 incompatibility group. The naphthalene biodegradation genes of P. fluorescens are highly homologous to each other. The study revealed a new group of the nahAc genes and two new variants of the nahG gene. The suggestion is made that the key genes of naphthalene biodegradation, nahAc and nahG, evolve independently and occur in P. fluorescens strains in different combinations.     

Molecular analysis of the Pseudomonas aeruginosa regulatory genes ptxR and ptxS.

We have previously described two Pseudomonas aeruginosa genes, ptxR, which enhances toxA and pvc (the pyoverdine chromophore operon) expression, and ptxS, the first gene of the kgu operon for the utilization of 2-ketogluconate by P. aeruginosa. ptxS interferes with the effect of ptxR on toxA expression. In this study, we have utilized DNA hybridization experiments to determine the presence of ptxR and ptxS homologous sequences in several gram-negative bacteria. ptxR homologous sequences were detected in P. aeruginosa strains only, while ptxS homologous sequences were detected in P. aeruginosa, Pseudomonas putida, and Pseudomonas fluorescens. Using Northern blot hybridization experiments and a ptxS-lacZ fusion plasmid, we have shown that P. aeruginosa ptxR and ptxS are expressed in P. putida and P. fluorescens. Additional Northern blot hybridization experiments confirmed that ptxS is transcribed in P. putida and P. fluorescens strains that carried no plasmid. The presence of a PtxS homologue in these strains was examined by DNA-gel shift experiments. Specific gel shift bands were detected when the lysates of P. aeruginosa, P. putida, and P. fluorescens were incubated with the ptxS operator site as probe. kgu-hybridizing sequences were detected in P. putida and P. fluorescens. These results suggest that (i) ptxR is present in P. aeruginosa, while ptxS is present in P. aeruginosa, P. putida, and P. fluorescens; (ii) both ptxR and ptxS are expressed in P. putida and P fluorescens; and (iii) a PtxS homologue may exist in P. putida and P. fluorescens.     

Nitrous oxide as end product of denitrification by strains of fluorescent pseudomonads.

Growing cultures of several strains of Pseudomonas fluorescens and Pseudomonas chlororaphis produced N2O as the only detectable gaseous product of denitrification, and other strains produced N2 as the gaseous end product of denitrification. All of the nitrogen in NO3- or NO2- added to cell suspensions of the N2O-producing strains P. fluorescens PJ 185 and P. chlororaphis B-560 was recovered as N2O. All of the nitrogen in NO3- or NO2- added to cell suspensions of the N2-producing strain P. fluorescens PJ70 was converted to N2. Cell extracts of P. fluorescens PJ 70, PJ 185, and P. chlororaphis B-560 exhibited NO3- reductase activity when sodium succinate was the electron donor. Reduced nicotinamide adenine dinucleotide and flavine adenine dinucleotide were required to demonstrate NO2- reductase activity in cell extracts.